I want to create an ebook that will be optimized for both iPhone and iPad, is there a solution to create one epub that will fit both iPad and iPhone.
Another thing, as for horizontal and vertical do I need to create two versions or does the epub can handle it by himself.
I hope by epub you mean DPS folio publication. You will need renditions to target diferrent devices screen resolution. You will need to publish different versions of folios and the viewer app will know which folio to pick it up according to the screen resolution of that device. For more help on folio renditions go here http://help.adobe.com/en_US/digitalpubsuite/using/WS9293e1fb3b977c5c-2 337961812e35738f56-8000.html